Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS65 KRIW 160500
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1000 PM MST MON DEC 15 2014

.SHORT TERM...TONIGHT THROUGH TUESDAY (ISSUED AT 255 PM MST)

WV IMAGERY SHOWING PROGRESSIVE WAVE PATTERN  WITH DEEP OCCLUDED LOW
TO THE E OVR NW MS...RIDGING TO THE WEST OF WY AND HEADED THIS
WAY...ANOTHER DEEP TROF OFF THE WRN CONUS COAST. STRONG JET AROUND
SRN PORTION OF TROF ALONG WITH MOISTURE/MID CLOUD AHEAD OF THIS FEATURE
ACROSS CA AND NV...ALL HEADED INTO THE WRN SIDE OF THE RIDGE. SFC
HAS LOW NEARLY DIRECTLY UNDER UPR LOW OVR NW MS...WITH ASSOCIATED
COLD FRONT TRAILING OFF TOT HE SW AND THRU OK AND NRN TX...THEN
STATIONARY FRONT BACKED UP AGAINST THE FRONT RANGE AND NWD AGAINST
THE WIND RIVER AND ABSAROKA MOUNTAINS.

WRN PORTION OF CCB EXTENDING WWD FROM NW OF THE MS LOW...ACROSS THE
CNTRL AND HI PLAINS AND INTO CNTRL WY IS ERODING QUICKLY FROM THE
WEST...WITH LIGHT PRECIP/SNOW EVAPORATING ALONG WITH IT. CLEARING
SKIES WITH SUNSHINE W OF THE DIVIDE. SEEMINGLY BENIGN YET TRICKY
FCST INCLUDES LOW/HI TEMPS...A FUNCTION AS OF CLOUD DISSIPATION THRU
THE EVENING...THEN POSSIBLE FOG FORMATION AS QUICK RADIATIONAL
COOLING FOLLOWS THE EROSION OF THE CLOUD DECK...FOLLOWED BY
POSSIBLE FOG DISSIPATION EARLY AS MID CLOUD INTRUDES UPON THE FA
FROM THE SW...OR WILL IT TRAP THE INVERSION TO SOME EXTENT ALLOWING
THE FOG TO PERPETUATE THROUGH MOST OF THE MORNING? ATTM....KEEPING
FOG E OF THE DIVIDE AROUND LONGER IN THE MORNING THAN WEST OF THE
DIVIDE. THIS IS DUE TO THE ARRIVAL OF INCREASED DEEPER MOISTURE
INJECTED INTO THE WRN CWA... LOWERING CLOUD BASES...AND INCREASING
CHANCES OF SNOW BY EARLY MORNING ACROSS THE WEST AS INCREASED LIFT
FROM BOTH TERRAIN AND PROXIMITY TO UPR JET ALLOWS FOR PRECIP AT THE
SFC. ATTM...ONLY LIGHT PRECIP/SNOW IS EXPECTED WITH THIS ACTIVITY
THRU THE EARLY FCST PERIOD...WITH ONLY 1 TO 3 INCHES OF NEW SNOW
EXPECTED ACROSS THE HIGH REACHES OF THE WIND RIVER...SALT AND
WYOMING RANGES BY TUE EVENING....AND LESS THAN AN INCH EVERYWHERE
ELSE WEST OF THE DIVIDE. CUT BACK SOME ON THE HI TEMPS FCST FOR TUE
AS INCREASED CLOUD COVER...ASSOCIATED WITH THE PREVIOUSLY MENTIONED
WX FEATURE...ACROSS MOST OF THE FA WILL KEEP THE REGION FROM WARMING
MUCH. MOST OF THE AREA E OF THE DIVIDE WITH BE FREE OF THE WRUNG OUT
PRECIP THROUGH THE FCST PERIOD.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY

THE NEXT MAIN TROUGH NOW OFF THE PACIFIC COAST OUT AT 135W WILL
EJECT THE FIRST SHORTWAVE ACROSS OUR AREA TUE NT AND WILL CONTINUE
TO PRODUCE SOME LIGHT SNOW OUT WEST WITH LIFT ENHANCED FROM THE
DIFLUENT SOUTHWEST FLOW ALONG WITH WEAK QG FORCING. SNOW FROM THIS
FEATURE SHOULD PERSIST OUT WEST THROUGH WEDNESDAY DURING THE
TROUPHPA. SNOW AMOUNTS SHOULD RANGE FROM AROUND 2 TO 3 INCHES IN THE
WESTERN MOUNTAINS WITH LOCALLY HIGHER AMOUNTS AND AND ONE TO TWO
INCHES IN THE WESTERN VALLEYS. THEN THE MAIN TROUGH WILL TRACK
ACROSS THE CWA THU NT/FRI. MORE SNOW CAN BE EXPECTED OUT WEST FROM
THIS FEATURE ON THU NT. SOME SNOW WILL SPILL OVER THE DIVIDE LATER
THU NT. AN ASCT VORT LOBE WILL TRACK SOUTHEAST ACROSS EASTERN IDAHO
THU NT RESEMBLING A FAVORABLE LANDER SNOW EVENT...ALBEIT QUICK
LIVED...SO PULLED SOME HIGHER POPS DOWN TO INCLUDE THE EAST SLOPE OF
THE WIND RIVER MTNS AND THE LANDER FOOTHILLS FOR EARLY FRIDAY
MORNING. A SHORT DRY PERIOD IS EXPECTED FRIDAY AFTERNOON AND FRIDAY
NT. THEN ON SATURDAY A CLOSED LOW WILL SCOOT EAST ACROSS SOUTHERN
CANADA AND WILL TIGHTEN THE WEST NORTHWEST DIFLUENT GRADIENT FOR
SOME UPSLOPE SNOW IN THE WEST. THEN ON SAT NT/SUNDAY THE GFS AND THE
EURO DIVERGE WITH THE GFS KEEPING THE INCREASING WEST NORTHWEST
UPSLOPE FLOW OVER WY WITH THE EURO SPLITTING THE FLOW TAKING THE
SOUTHERN STREAM LOW WAY DOWN TO THE MEXICAN BORDER AND THE NORTHERN
STREAM WEST NORTHWEST FLOW TO THE NORTH OVER MT. NEED MORE RUN TO
RUN AND MODEL CONSISTENCY TO MAKE ANY WHOLE SALE CHANGES TO POPS FOR
SUN SO WILL KEEP THE IDEA OF CHC POPS OVER THE SOUTHWEST SUNDAY
TAKING INTO ACCOUNT THE SPLITTING SOUTHERN STREAM ENERGY. KEPT POPS
IN THE NW ON MONDAY WITH THE WEST NORTHWEST UPSLOPE FLOW AS
ADVERTISED BY BOTH THE GFS AND THE EURO. NO GREAT TEMP CHANGES
EXPECTED THROUGH THE PERIOD WITH SEASONABLY COOL TEMPS EXPECTED.

&&

.AVIATION.../06Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

AREAS OF LOW CLOUDS AND FOG WILL OCCUR THROUGH 15Z WITH MVFR TO IFR
CONDITIONS. AFTER 15Z VFR CONDITIONS WILL PREVAIL OVER THE REGION.
SOME LIGHT SNOW WILL OCCUR OVER THE ABSAROKA AND WIND RIVER
MOUNTAINS AFTER 09Z AND CONTINUE OFF AND ON THROUGH 06Z WED. EXPECT
MOUNTAINS TO BE OBSCURED FROM TIME TO TIME WITH MVFR/IFR CONDITIONS.
ISOLATED SNOW SHOWERS ARE POSSIBLE OVER THE LOWER ELEVATIONS AFTER
12Z TUE THROUGH 06Z WED.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

CLOUDS WILL INCREASE AND LOWER OVERNIGHT. SNOW SHOWERS WILL OCCUR IN
THE WESTERN MOUNTAINS THROUGH MUCH OF THE PERIOD. SNOW SHOWERS WILL
OCCUR AT TIMES IN THE WESTERN VALLEYS OVERNIGHT THROUGH TUESDAY INTO
TUESDAY NIGHT. EXPECT AREAS OF MVFR CONDITIONS THROUGH 06Z WED WITH
LOCAL IFR. MOUNTAINS WILL BE FREQUENTLY OBSCURED. PLEASE SEE
INDIVIDUAL TERMINAL FORECASTS FOR DETAILS.

&&

.FIRE WEATHER...

WINTER RETURNING TO THE FORECAST AREA OVER THE WEEKEND WILL ALLOW
FOR RH VALUES TO REMAIN ELEVATED FOR SEVERAL DAYS OVER THE NEW
SNOWPACK. SNOW EVEN WITH WINDS INCREASING OUT OF THE SOUTHWEST
TUESDAY AND WEDNESDAY...FIRE DANGER WILL REMAIN LOW THROUGH THIS
PERIOD. HOWEVER...AS MUCH AS THE NEW SNOW WILL HELP IN KEEPING THE
RH VALUES UP...IT WILL ALSO PARTIALLY BE RESPONSIBLE FOR POOR SMOKE
DISPERSION OVER THESE SAME SURFACES FOR THE NEXT SEVERAL DAYS ACROSS
MUCH OF THE AREA. LOCATIONS THAT WILL STAND THE BEST CHANCE AT
PARTIALLY MIXING OUT...DUE TO WINDS ALOFT BUILDING DOWNWARD...WILL
OCCUR OVER THE HIGHER MOUNTAINS OF THE WEST...ACROSS PORTIONS OF
SWEETWATER COUNTY...AND PERHAPS FROM EAST OF SOUTH PASS THROUGH
NATRONA COUNTY...BUT ONLY FOR A VERY SHORT PERIOD OF TIME IN THE
AFTERNOONS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...BRAUN
LONG TERM...LIPSON
AVIATION...AR
FIRE WEATHER...BRAUN







USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.